Ipotesi\!:\ ABC\ Triangolo\
Tesi\!:\ \overline{AB} < \overline{AC} + 
\overline{CB};\ \overline{BC} > \overline{AB} - 
\overline{AC}

1\ -\ \overline{BC} \cong \overline{CD}\ -\ 
Per\ costruzione

2\ -\ C\^BD \cong C\^DB\ -\ Angoli\ alla\ base\ 
di\ un\ triangolo\ isoscele

3\ -\ C\^BD < A\^BD\ -\ Per\ costruzione\ C\ è\ 
interno\ ad\ \overline{AD}

4\ -\ A\^BD > C\^DB\ -\ Per\ (2)\ e\ (3)

5\ -\ \overline{AD} > \overline{AB}\ -\ Terorema\ 
lati\ triangolo\ con\ angoli\ disuguali

6\ -\ \overline{AD} = \overline{AC} + 
\overline{CD}\ -\ Per\ costruzione

7\ -\ \overline{AB} < \overline{AC} + 
\overline{CB}\ -\ Per\ (5),\ (6)\ e\ (1)\ -\ Prima\ 
parte\ tesi

8\ -\ \overline{CD} = \overline{AD} - 
\overline{AC}\ -\ Vedi\ (6) 

9\ -\ \overline{CD} > \overline{AB} -
\overline{AC}\ -\ Per\ (8)\ e\ (5)

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10\ -\ \overline{BC} > \overline{AB} - 
\overline{AC}\ -\ Per\ (9)\ e\ (1)\
Q.\ E.\ D.

A = (-1.1, -2.62)
B = (4.12, -2.62)
C = (1.04, -0.4)
poli1, c, a, b = Polygon(A, B, C)
d = Ray(A, C)
D = Intersect(Circle[C, a], d)
e = Segment(C, D)
f = Segment(C, B)
g = Segment(B, D)
α = Angle(C, D, B)
β = Angle(C, B, D)
γ = Angle(A, B, D)